feat(nodes): traffic-writer queue, full-mirror sync, WS event fixes

- Traffic-writer single-consumer queue (web/service/traffic_writer.go)
  serialises every DB write that touches up/down/all_time/last_online
  (AddTraffic, SetRemoteTraffic, Reset*, UpdateClientTrafficByEmail) so
  overlapping goroutines can no longer clobber each other's column-scoped
  Updates with a stale tx.Save.

- DB pool: WAL + busy_timeout=10s + synchronous=NORMAL + _txlock=
  immediate, MaxOpenConns=8 / MaxIdleConns=4. The immediate-tx PRAGMA
  fixes residual "database is locked [0ms]" cases where deferred-tx
  writer-upgrade conflicts bypass busy_timeout.

- SetRemoteTraffic full-mirrors node-authoritative state into central:
  settings JSON, remark, listen, port, total, expiry, all_time, enable,
  plus per-client total/expiry/reset/all_time. Inbounds and
  client_traffics rows present on node but missing from central are
  created; rows missing from snap are deleted (with cascading
  client_traffics removal).

- NodeTrafficSyncJob detects structural changes from the mirror and
  broadcasts invalidate(inbounds) so open central UIs re-fetch via REST
  on node-side add/del/edit without manual refresh.

- XrayTrafficJob broadcasts invalidate(inbounds) when auto-disable flips
  client_traffics.enable so the per-client toggle reflects depletion
  without manual refresh.

- Frontend: inbounds page now subscribes to the BroadcastInbounds 'inbounds'
  WS event (full-list pushes from add/del/update controllers were silently
  dropped). Fixes invalidate payload field (dataType -> type). Restart-
  panel modal switched from Promise-wrap to onOk-only so Cancel actually
  cancels.

- Node files trimmed of stale prose-comments; cron cadence dropped
  10s -> 5s to match the inbounds page UX.

- README badges and Go module path bumped v2 -> v3 to match module rename.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

web/websocket/hub.go

@@ -43,8 +43,8 @@ const (
 	// rapid mutations cannot drown the hub. Bursts within the interval are
 	// dropped (not coalesced); the next broadcast outside the window delivers
 	// the latest state. Only message types in throttledMessageTypes are gated —
-	// heartbeat and real-time signals (status, traffic, client_stats,
-	// notification, xray_state, invalidate) bypass this so they are never delayed.
+	// heartbeat and one-shot signals (status, notification, xray_state,
+	// invalidate) bypass this so they are never delayed.
 	minBroadcastInterval = 250 * time.Millisecond
 
 	// hubRestartAttempts caps panic-recovery restarts. After this many
@@ -103,19 +103,13 @@ func NewHub() *Hub {
 	}
 }
 
-// throttledMessageTypes is the explicit allow-list of message types subject to
-// the per-type rate limit. Everything else (status, traffic, client_stats,
-// notification, xray_state, invalidate) is heartbeat- or signal-class and must
-// not be delayed. Keeping the set explicit (vs. an exclusion list) makes the
-// intent obvious when new message types are added — by default they bypass.
 var throttledMessageTypes = map[MessageType]struct{}{
-	MessageTypeInbounds:  {},
-	MessageTypeOutbounds: {},
+	MessageTypeInbounds:    {},
+	MessageTypeOutbounds:   {},
+	MessageTypeTraffic:     {},
+	MessageTypeClientStats: {},
 }
 
-// shouldThrottle returns true if a broadcast of msgType is rate-limited and
-// happened within minBroadcastInterval of the previous one. Only message types
-// in throttledMessageTypes are gated.
 func (h *Hub) shouldThrottle(msgType MessageType) bool {
 	if _, gated := throttledMessageTypes[msgType]; !gated {
 		return false